The present invention relates to methods and systems for reducing moisture damage to a building which has a crawl space in the foundation.
Many buildings, especially smaller homes, have a foundation with a crawl space. This crawl space provides access to utility connections and other structural features of the building for periodic servicing. In most cases, the majority of the crawl space is underground, and has a predominantly soil floor usually 18-24 inches in depth. However, gravel and other fill materials--including leftover construction materials and trash--are often found on or embedded in the crawl space floor. Occasionally, the crawl space floor may include a concrete slab.
Unfortunately, the ground water table is often high enough in poorly drained soils that at least a portion of the crawl space is below it. As a result, ground water is consistently present at some level within the crawl space causing an excessive moisture problem. These wet crawl spaces encourage mold and fungus growth which decays wood structure exposed to the moisture, such as floor joists and subflooring. In addition, unpleasant odors often result. Furthermore, when the problem is so severe that water stands in the crawl space, the situation may pose a health risk.
To address this problem, some builders install a moisture barrier, such as a sheet of thick plastic, over the floor of the crawl space. Although this moisture barrier can reduce exposure to moisture present in small amounts in well-drained soil, it does not provide for the removal of excessive water common to a truly "wet" crawl space. In fact, a vapor barrier without a removal system often intensifies the problem because water becomes trapped on top of it.
One way to solve this problem is by installing a drain tile in a trench, and connecting this trench to a sump pit system. This approach includes excavating a trench along the inner perimeter of the crawl space. This trench intersects the sump pit system and is configured to receive the drain tiles. The trench is back filled with an aggregate which surrounds the drain tiles. Commonly, the sump pit is surrounded by aggregate. The drain tiles collect water laterally from the crawl space floor and adjacent walls for drainage into the sump pit, and the porous nature of the surrounding aggregate displaces excess water for collection in the sump pit. The sump pit system may include a pump and connected conduit through which water is pumped away from the building when it exceeds a predetermined level within the pit. A similar system is shown in U.S. Pat. No. 3,562,982 52/169.5, 169.14, 302.3 to Parezo which is hereby incorporated by reference. Notably, this system does not remove all the water present in the crawl space nor does it eliminate the need for a moisture or vapor barrier. Instead, this system controllably removes excess water in the crawl space and keeps it under the vapor barrier so that the remainder of the building is not exposed to the troublesome excess moisture.
While this system is effective, it can often be costly to install once the building has been built. One aspect adding to the cost is the movement of the aggregate into the crawl space and the laborious task of arranging it therein. Specifically, because of the limited dimensions of a crawl space (a height of generally less than four feet) all the foundation vents are usually removed to install gravel shoots, and the gravel is moved within the crawl space to desired locations by hand shoveling or with a sled.
In cases were the moisture problem is not severe, a less complex drain system which does not use drain tiles may suffice. Even the excavation of a trench may not be needed in some cases. Unfortunately, these alternative systems require additional aggregate to perform correctly. The current labor intensive method of placing aggregate in the crawl space prevents these alternative systems from being cost effective. Consequently, what is needed is a way to reduce the cost of installing existing drain tile trench systems as well as a way to make alternative systems cost effective.